docs: def infer_order(self, goal, **kwargs):
          """Infer an order in order to obtain an effect close to goal, given the
          observation data of the model.
  
          :arg goal:  a goal vector compatible with self.Sfeats
          :rtype:  same as goal (if list, tuple, or pandas.Series, else tuple)
          """
          x = self.imodel.infer_x(np.array(self._pre_y(goal)), **kwargs)[0]
          return self._post_x(x, goal)